; chapter4 exercise 1 
(defun quarter-turn (sa)
		(let* ((d (array-dimensions sa)) (t-sa (make-array d)))
			(do ((i 0 (+ 1 i)))
				((= i (car d)) t-sa)
				(do* ((j 0 (+ 1 j)))
					((= j (nth 1 d)) 'done)
					(setf (aref t-sa j (- (car d) i 1)) (aref sa i j))))))


(setf sa #2A((A B C) (D E F) (G H I)))
